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Birds. Bird Taxonomy. Kingdom: Animalia Phylum: Chordata Subphylum: Craniata Infraphylum : Vertebrata Class: Aves Ornithology- study of birds. Characteristics of Birds. Adaptations for flight Appendages modified as wings Feathers
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Bird Taxonomy • Kingdom: Animalia • Phylum: Chordata • Subphylum: Craniata • Infraphylum: Vertebrata • Class: Aves • Ornithology- study of birds
Characteristics of Birds • Adaptations for flight • Appendages modified as wings • Feathers • Endothermic- ability to maintain constant body temperature • High metabolic rate • Vertebral column modified for flight • Bones lightened by numerous air sacs • Lay amniotic eggs • Breathe with lungs • Legs are covered in scales
Birds & Their Relatives • Birds are classified as “avian reptiles”…or informally called “glorified reptiles” • Differences from reptiles: • Have a horny bill • Lack teeth • Similarities with reptiles: • Single occipital condyle on the skull (where the skull meets the vertebrae) • Single ear ossicle • Lower jaw structure • Nucleated red blood cells • Liver & kidney function • Formation of nests for eggs
Bird & Reptile Relationship • Birds descended from ancient archosaurs (same ancestor as dinosaurs & crocodiles) • Closely related to the theropod dinosaur lineage (also shared with the Tyrannosaurus Rex and the Velociraptor) • Several ancient theropods had feathers
Evolution of Flight • Archaeopteryx- first fossil of an ancient bird • Long reptilian tail and claws • Short, rounded wings • Feathers on the tail • Lived during the Jurassic period (150 mya) • Early winged reptiles used wings to either bat flying insects or trap prey against the ground • Wings developed to help stabilize dinosaurs during horizontal jumps • Over time, the wings evolved to allow for flight (larger flight muscles developed)
Diversity of Modern Birds • 9,100 species • 27 orders of birds • Species differ based on…… • Behaviors • Songs • Anatomical differences • Ecological niches (role in the environment)
External Structures- The Feathers • Plumage- covering of feathers • 2 Functions of Feathers in Flight… • Form the flight surfaces that provide lift and aid steering • Prevent excessive heat loss • Function in courtship, incubation, & waterproofing Birds of Paradise
Feathers • Feathers are modified reptilian scales that develop from tiny pits, called follicles, in the skin. • Just as snakes and lizards replace their skin by molting, birds molt and replace their feathers. • However, few birds shed all of their feathers at one time.
Feathers • Birds have two main types of feathers: contour feathers and down feathers. • Contour feathers cover the bird’s body and give adult birds their shape. • Specialized contour feathers, called flight feathers, are found on a bird’s wings and tail. • These feathers help provide lift for flight.
Feathers • A contour feather has many branches called barbs. • Each barb has many projections, called barbulesthat are equipped with microscopic hooks. • These hooks link the barbs to one another, giving the feather a continuous surface and a sturdy flexible shape.
Feathers • With use, the connections of the hooks and barbs become undone. • When you see a bird pulling its feathers through its beak, it is relinking these connections. • This process is called preening. • Most birds have a gland called a preen gland which secretes oil. • When a bird preens, it spreads the oilover its feathers, cleaning and waterproofingthem.
Feathers • Down feathers cover the body of young birds and are found beneath the contour feathers of adults. • Their soft, fluffy structure provides good insulation for the bird, helping the bird conserve body heat.
Feathers • There are other reasons that feathers are important to birds. • Their coloration may be protective (as camouflage) or may be important in the selection of a mate. • The feathers of some birds allow them to blend in with their surroundings. • In some species, the males develop special plumage during the breeding season.
Avian Skeleton • The bones of birds are thin and hollow. • Many of the bones are fused, making a bird’s skeleton more rigid than a reptile’s. • The fused sections form a sturdy frame that anchors muscles during flight.
Avian Skeleton and Muscles • The power for flight (or for swimming underwater, like penguins) comes from large breast muscles that can make up to 30% of a birds body weight. • These muscles stretch from the wings to the breastbone. • The breastbone is greatly enlarged and bears a prominent keel for muscle attachment. • Muscles also attach to the fused collarbones (wishbone). • No other living vertebrates have a keeled breastbone or fused collarbones.
Endothermic Metabolism • Birds are endotherms; they generate enough heat through metabolism to maintain a high body temperature. • Birds maintain body temperatures ranging from 40°C to 42°C (104°F to 108°F), which is higher than the body temperature of most mammals. • These high temperatures are due to a high rate of metabolism, which satisfies the increased energy requirements of flight.
Avian Heart Structure • The ventricle of birds is completely divided by a septum. • Oxygen-rich and oxygen-poor blood is kept separate, meaning that oxygen is delivered to the body cells more efficiently. • The sinus venosus, which is a prominent part of the fish heart, is not a separate chamber of the heart in birds (or mammals). • However, a small amount of tissue from it remains in the wall of the right atrium. • This tissue is the point of origin of the heartbeat and is known as the heart’s pacemaker.
Avian Lungs • Birds use a considerable amount of energy when they fly. • Since birds often fly for long periods of time, their cellular demand for energy exceeds that of even the most active mammals. • To increase the efficiency of lungs, birds have air pass over the respiratory surface in one direction only. • One-way air flow is possible in birds because they have air sacs connected to their lungs. • There is no gas exchange in the air sacs, they act as holding tanks.
Avian Lungs • There are two important advantages to one-way air flow. • First, the lungs are exposed only to air that is almost fully oxygenated, increasing the amount of oxygen transported to the body cells. • Second, the flow of blood in the lungs runs in a different direction than the flow of air does. • The difference in direction increases oxygen absorption.
Avian Digestive System • Large meals are temporarily stored in the crop, the expandable lower portion of the esophagus. • The food then passes into a two-chamber stomach. • In the first chamber, stomach acids begin breaking down the food. • The partially digested food is then passed to the second chamber, the gizzard, where it is ground and crushed. • Undigested material is eliminated through the cloaca.
Avian Excretory System • The excretory system is efficient and lightweight. • It does not store waste liquids in a bladder. • Instead, birds convert nitrogenous waste to uric acid, which is concentrated into a harmless white paste. • The uric acid travels to the cloaca and is eliminated.
